The present invention is directed to a drywall trimming element. More particularly, the present invention pertains to a drywall trimming element having a compound locking feature to enhance the bond between the element and the compound.
Drywall trimming elements are used at the intersection of drywall planes. For example, a drywall trimming element can be used at the intersection of two planes that define an outer corner. The trimming elements protect the edges and corners of the drywall from bumps, abrasions and damage. Trimming elements can also be used at inside corners (intersections that define an acute angle), to provide a smooth and visually appealing finish, as well as to protect the inside corner from damage.
Outside trimming elements are presently made, in one form, from metal. The metal corner bead includes an elongate corner, typically rolled or bent, and a pair of flanges or legs extending from the corner at about a 90 degree angle. To set these metal corner beads in place, the bead is fastened to the support behind the wall board (such as a wood stud) by screws, nails or the like through the legs. One or more layers of joint compound are applied over the bead, from the corner outwardly, over the legs, and smoothed to the wall surface (referred to as feathering), to eliminate any visual distinction from the corner to the wall surface.
While metal corner beads do in fact protect the drywall corners from damage, they too can be subject to damage, for example, when bumped or struck. In addition, the adhesion or bonding of the compound to the metal bead is limited. As such, with even a minor strike of the bead, the compound can separate from the bead resulting in a crack, crevasse or open spot at the corner bead.
Extruded plastic moldings have come into greater use (over metal) for a number of reasons. First, is their ease of use—they are easy to install, cut (when necessary) and fit to a corner. They are also much more “forgiving” and less subject to unwanted bending than metal when being stored and handled. Moreover, extruded materials will not discolor (e.g., rust) or corrode when subject to less than ideal or controlled environmental conditions.
It has also been found that extruded materials (moldings) can be formed into a wide variety of shapes and sizes. As such, extruded materials are used to form large radius corner elements, such as that disclosed in Koenig, Jr., et al., U.S. Pat. No. 6,691,477, crown moldings and crown-type moldings, as disclosed in Koenig, Jr., et al., U.S. Pat. No. 7,200,970, and archway moldings, as disclosed in Koenig, Jr., et al., U.S. Pat. No. 6,119,420, all of which are commonly assigned with the present application and all of which are incorporated herein by reference.
In order to secure the elements and moldings to the drywall, one or both of the legs of the elements and molding have openings therein. A fastener can be used to secure the element to the wall and one or more layers of joint compound are applied over the legs to create a smooth transition from the element to the wall surface. In some installations, the element is installed without the fastener, in which case a layer of joint compound is applied to the wall and the element is pressed into the wet joint compound. The openings in the element allow for the flow of joint compound therethrough which, when dried, hardens to secure the element to the wall.
Even though the hardened joint compound bonds well to and secures the element to the wall, it has been observed that when the element is struck a relatively hard blow, the compound will crack and the element can separate from the wall. While minor cracks can generally be readily fixed with sanding and applications of fresh compound (with intermediate sanding) and painting, if the element separates from the wall, repair is usually not so readily accomplished. That is, when the element separates from the wall, dried compound may fall from the wall or element and prevent the element from lying flush on the wall. This can result in the element bulging from the wall at locations where compound has collected between the element and the wall. It has also been observed that cracking and the like often occurs during settling of a wall/structure.
It has also been found that with substantial blows to the element, exterior compound can separate from the element. While this is readily repaired, the more cracking or chipping that occurs, the more repair that it required.
Accordingly, there is a need for a drywall trimming element that secures to a drywall with a high degree of integrity. Desirably, such an element permits being readily secured to the wall with compound such that the compound will not loosen from the element when struck. More desirably, such an element includes provisions to “lock” the compound to the element in such a manner as to withstand a substantial blow.